Pozzo Thierry, Stapley Paul J, Papaxanthis Charalambos
ERITm/INSERM, Université de Bourgogne, Dijon, France.
Exp Brain Res. 2002 Jun;144(3):343-50. doi: 10.1007/s00221-002-1052-6. Epub 2002 Apr 13.
We examined the coordination between equilibrium and voluntary pointing movements executed from the standing position, using the whole body. It has previously been shown that trunk movement has little effect upon kinematic characteristics of hand pointing when movements are executed in the sitting position. The present study asked if elements of hand trajectory are modified by requirements of large trunk displacements and fine equilibrium control when pointing movements are executed from the standing position. To achieve this, center of pressure (CoP) and center of mass (CoM) displacements were analyzed along with the kinematics of the pointing hand. Results showed that the CoM was not stabilized (it displaced between 23% and 61+/-21% of the foot's length), confirming that instead of a compensation of mechanical perturbations due to arm and trunk movements, the present equilibrium strategy consisted of controlling CoM acceleration towards the target. Hand paths were curved and were not distance or speed invariant. Rather than simple inefficiencies in programming or execution, path curvature suggested that different hand movement strategies were chosen as a function of equilibrium constraints. In light of these results, we hypothesize that postural stability may play a role in the generation of hand trajectory for complex, whole-body pointing movements, in addition to constraints placed upon end-effector kinematics or the dynamic optimization of upper-limb movements. A dependent regulation of equilibrium and spatial components of the movement is proposed.
我们使用全身来研究从站立姿势执行的平衡与自主指向运动之间的协调性。先前的研究表明，当在坐姿下执行运动时，躯干运动对手部指向的运动学特征影响很小。本研究探讨了从站立姿势执行指向运动时，手部轨迹的要素是否会因大幅度躯干位移和精细平衡控制的要求而发生改变。为了实现这一点，我们分析了压力中心（CoP）和质心（CoM）的位移以及指向手的运动学。结果表明，质心并未稳定（其位移幅度在足长的23%至61±21%之间），这证实了当前的平衡策略并非补偿手臂和躯干运动引起的机械扰动，而是包括控制质心向目标的加速度。手部路径是弯曲的，且与距离或速度无关。路径曲率并非简单地表明编程或执行效率低下，而是表明根据平衡约束选择了不同的手部运动策略。鉴于这些结果，我们假设姿势稳定性可能在复杂的全身指向运动的手部轨迹生成中发挥作用，这除了对末端执行器运动学的约束或上肢运动的动态优化之外。我们提出了运动的平衡和空间成分的依赖调节。
